Tag: chemistry

Questions Related to chemistry

Aluminium is extracted from alumina $(Al _2O _3)$ by electrolysis.

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. True

  2. False

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Correct Option: A
Explanation:

The given statement is true as $Al$ is extracted from alumina($ Al _{2}O _{3}$) by the process of electrolysis.

Impure bauxite on reaction with $NaOH$ gives _____________.

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. $Al(OH) _3$

  2. $NaAlO _2$

  3. $Al _2O _3$

  4. All of the above

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Correct Option: B
Explanation:

$Al _2O _3+2NaOH\longrightarrow 2NaAlO _2+H _2O$

In the electrolytic reduction of alumina, the electrolyte is covered with coke powder because, if :

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. prevents oxidation of aluminium formed

  2. reacts with aluminium forming aluminium carbide

  3. prevents heat loss from electrolyte

  4. None of the above

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Correct Option: C
Explanation:

The electrolyte is a molten bath of cryolite and dissolved alumina. Cryolite is a good solvent for alumina with low melting point. The molten electrolyte is maintained at high temperature inside the insulating cell by using high amount of coke powder or dust to prevent the heat loss.

Aluminium is extracted by :

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. Heating sodium aluminium silicate to a high temperature

  2. Treating cryolite with sodium hydroxide solution under pressure

  3. Heating aluminium oxide with coke in a furnace

  4. The electrolysis of molten aluminium oxide in fused cryolite

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Correct Option: D
Explanation:

Aluminium is extracted by electrolysis. The ore is first converted into pure aluminium oxide by the Bayer Process and this is then electrolysed in solution in molten cryolite another aluminium compound. The aluminium oxide has too high a melting point to electrolyse on its own. The usual aluminium ore is bauxite.

The electrolyte used in electrolytic refining of impure aluminium is:

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. $AlF _3 + CaF _2$

  2. $Na _3AlF _6 + CAF _2$

  3. $AlF _3, Na _3AlF _6$ and $CaF _2$

  4. Any aluminium salt is molten state

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Correct Option: C
Explanation:

The electrolytes are used to reduce melting point and increase conductivity.

$\therefore $ The electrolytes are $AlF _{6} , Na _{3}AlF _{6} , CaF _{2}$.

$NaAlO 2$ on hydrolysis gives ________.

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. $NaOH$

  2. $Al _2O _3$

  3. both $A$ and $B$

  4. none of the above

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Correct Option: C
Explanation:

$NaAlO _2$ on hydrolysis gives sodium hydroxide and $Al _2O _3$.

$2NaAlO _2 + H _2O \rightarrow Al _2O _3 + 2NaOH$

During electrolysis of aluminium, which of the following substance is used as an electrolyte?

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. $Al _2O _3$

  2. $Al _2O _3, Na _3AlF _6$

  3. $Al _2O _3, Na _3AlF _6, CaF _2$

  4. None of the above

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Correct Option: C
Explanation:

The substance which is used as an electrolyte during electrolysis of aluminium is $Al _2O _3, Na _3AlF _6, CaF _2$.

Anodic product in the electrolytic reduction of alumina:

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. $CO _2, O _2$

  2. $O _2$

  3. $F _2$

  4. $O _2,F _2$

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Correct Option: B
Explanation:

Ionization of Alumina in Electrolytic refining.

$2Al _2O _3\longrightarrow 6O^{-2}+Al^{3+}$
Reaction at cathode
$4Al^{3+}+12e^{-}\longrightarrow 4Al$
Reaction at anode
$6O^{-2}\longrightarrow 3O _2+12e^-$
$O _2$ is released at anode.

The most abundant metal in the earths crust is:

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. silver

  2. aluminium

  3. zinc

  4. iron

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Correct Option: B
Explanation:

Most abundant metal on the earth's crust is Aluminium.

Aluminium is extracted mainly from its principal ore :

chemistry production of metals extraction of aluminium metallurgy of aluminium extraction of metals by electrolysis

  1. magnetite

  2. kaolinite

  3. bauxite

  4. haematite

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Correct Option: C
Explanation:

Naturally occurring aluminium is a major component of silicates such as mica and clay. Aluminium is extracted mainly from its principal ore bauxite.